LOSS AND LOSS ADJUSTMENT RESERVES - (Schedule of Cumulative Paid Losses and ALAE, Net of Reinsurance Recoverable) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Claims Development [Line Items]
Unfavorable loss and LAE reserve	$ 324,362	$ 296,230	$ 230,515	$ 158,110
Homeowners [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	958,755
Unfavorable loss and LAE reserve	137,168
Homeowners [Member] | Accident Year 2010 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	30,585	30,449	30,376	29,739	$ 29,092	$ 27,984		$ 26,886	$ 24,730	$ 21,350	$ 14,052
Homeowners [Member] | Accident Year 2011 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	26,340	26,287	25,982	25,580	24,047	22,723		21,323	19,250	11,119
Homeowners [Member] | Accident Year 2012 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	26,861	26,777	26,113	25,186	23,923	23,120		20,728	13,693
Homeowners [Member] | Accident Year 2013 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	37,688	37,473	35,803	35,123	33,867	31,606		19,986
Homeowners [Member] | Accident Year 2014 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	61,441	60,555	59,722	57,891	53,831	37,033
Homeowners [Member] | Accident Year 2015 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	92,327	90,415	86,647	79,359	52,214
Homeowners [Member] | Accident Year 2016 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	152,258	148,274	142,716	102,556
Homeowners [Member] | Accident Year 2017 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	179,327	176,580	135,589
Homeowners [Member] | Accident Year 2018 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	194,160	141,173
Homeowners [Member] | Accident Year 2019 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	157,768
Homeowners [Member] | Acquired balance from acquisition
Claims Development [Line Items]
Unfavorable loss and LAE reserve	11,825
Homeowners [Member] | All outstanding liabilities for unpaid claims and ALAE prior to 2010, net of reinsurance
Claims Development [Line Items]
Unfavorable loss and LAE reserve	3
Commercial General Liability [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	49,254
Unfavorable loss and LAE reserve	17,014
Commercial General Liability [Member] | Accident Year 2010 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	8,165	7,918	7,631	7,382	7,238	6,363	$ 5,553	3,855	2,279	1,187
Commercial General Liability [Member] | Accident Year 2011 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	7,365	6,349	5,831	4,866	4,246	3,673	3,366	2,763	764
Commercial General Liability [Member] | Accident Year 2012 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	4,521	4,098	3,841	3,686	3,342	2,632	1,714	871
Commercial General Liability [Member] | Accident Year 2013 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	5,467	5,033	4,606	3,867	3,366	2,233	882
Commercial General Liability [Member] | Accident Year 2014 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	6,270	5,130	4,375	3,855	2,593	717
Commercial General Liability [Member] | Accident Year 2015 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	5,866	3,827	3,249	2,296	798
Commercial General Liability [Member] | Accident Year 2016 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	6,606	5,088	3,657	1,515
Commercial General Liability [Member] | Accident Year 2017 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	3,293	2,478	1,592
Commercial General Liability [Member] | Accident Year 2018 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	1,554	963
Commercial General Liability [Member] | Accident Year 2019 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	147
Commercial General Liability [Member] | All outstanding liabilities for unpaid claims and ALAE prior to 2010, net of reinsurance
Claims Development [Line Items]
Unfavorable loss and LAE reserve	1,416
Personal Auto Liability [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	69,691
Unfavorable loss and LAE reserve	2,142
Personal Auto Liability [Member] | Accident Year 2010 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	3,037	3,037	3,035	2,984	2,978	2,942	2,863	2,715	2,482	$ 1,713
Personal Auto Liability [Member] | Accident Year 2011 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	2,755	2,755	2,755	2,755	2,726	2,644	2,562	2,381	$ 1,417
Personal Auto Liability [Member] | Accident Year 2012 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	1,447	1,444	1,430	1,393	1,384	1,333	1,293	$ 867
Personal Auto Liability [Member] | Accident Year 2013 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	2,116	2,112	2,109	2,069	1,906	1,609	$ 907
Personal Auto Liability [Member] | Accident Year 2014 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	4,383	4,291	4,122	3,678	3,120	$ 1,455
Personal Auto Liability [Member] | Accident Year 2015 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	2,890	2,807	2,670	2,293	$ 1,393
Personal Auto Liability [Member] | Accident Year 2016 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	25,582	23,053	17,258	$ 8,084
Personal Auto Liability [Member] | Accident Year 2017 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	23,860	20,762	$ 12,821
Personal Auto Liability [Member] | Accident Year 2018 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	3,626	$ 2,331
Personal Auto Liability [Member] | Accident Year 2019 [Member]
Claims Development [Line Items]
Cumulative paid, claims and allocated claim adjustment expenses, net of reinsurance	(5)
Personal Auto Liability [Member] | All outstanding liabilities for unpaid claims and ALAE prior to 2010, net of reinsurance
Claims Development [Line Items]
Unfavorable loss and LAE reserve	$ 9